1. Field of the Invention
The present invention relates to a turbomolecular pump including a plurality of alternatingly arranged rotor and stator discs, and a plurality of spacer rings for spacing the stator discs from each other, with the stator discs and the spacer rings forming a stator stack.
2. Description of the Prior Art
Active pump elements of a turbomolecular pump consist of rotor and stator discs which are provided with vanes and which are alternatingly arranged one behind the other. Generally, each of the stator and rotor discs has a support disc which supports an outer member provided with vanes. The vanes of the rotor discs, which rotate with high speed, together with the stator vanes, provide a pumping effect. The stator discs are spaced from each other by spacer rings which are provided between the stator discs at the outer circumferences of the stator discs. The spacing between the stator discs insure a contact-free rotation of the rotor discs between the stator discs. The stator discs and the spacer rings form a stator package or a stator stack which is centered by the inner wall of the pump housing. The stator package or stack can include, e.g., springs for axially biasing the stator discs and spacer rings toward each other so that a rigid connection is formed therebetween.
To provide for a precise assembly of stator discs, spacer rings, and other elements of the stator stack, repeated adjustments need be made in order to compensate the manufacturing tolerances. This noticeably increases the time connected with manufacturing of the stator components and with the assembly of the stator.
By providing an O-ring, e.g., formed of Viton(copyright), between the spacer ring adjacent to the forevacuum side and the lower part of the pump, a partial compensation of the manufacturing tolerances can be achieved.
One of the drawback of the above-discussed compensation of the manufacturing tolerances consists in a very bad heat conductivity of the O-ring material. As a result, during the operation of the pump, the heat, which is generated inside the pump, is only partially transmitted to the pump housing and the lower part of the pump. In addition, during pumping of aggressive media, the insufficient corrosion resistance of the O-ring material presents a problem. In addition, because of the high degasifying rate, this O-ring cannot be used on the high vacuum side.
French Patent No. 2,683,277 discloses means for simplifying the assembly and maintenance of this type of pumps. According to the French patent, the intermediate, adjacent to the high vacuum side, ring is provided with a sharp, knife-shaped edge, which becomes deformed during the formation of the stator stack, compensating, thus, the manufacturing tolerances. In this case, the material of the stator elements and the spacer ring should be the same.
An object of the present invention is to provide, in a turbomolecular pump, means which would permit to compensate manufacturing tolerances of separate components of the stator stack and which would be devoid of drawbacks of the prior art means.
Another object of the present invention is to provide, in a turbomolecular pump, manufacturing tolerances compensating means which would afford a greater freedom in the selection of their material and would insure a better heat conductivity.
These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing at least one elastically deformable metallic element between at least two spacer rings and which also forms part of the stator stack.
The elastically deformable metallic element or member compensates, during assembly of the stator, the manufacturing tolerances. The elastically deformable metallic member insures precise spacing between the rotor and stator components. The use of the elastically deformable metallic member permits to eliminate the time-consuming adjustments taking place during assembly of a conventional pump. The elastically deformable metallic member can be used in any region of the pump, including the high vacuum side of the pump. By selecting a suitable metallic material for forming the elastically deformable member, it can be made insensitive to aggressive media. By the metallic contact of the elastically deformable member with other components, heat removal can be favorably influenced. Moreover, by providing an elastically deformable member having different shapes and formed of different materials, it is possible to vary the heat conductance.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.